Yes but it changes with pH. My well water runs pH 6.4 usually and has alkalinity of 80. If I want to bring that to pH 5.5, to use the same example, I need 1.24 mEq/L of acid which, compared to the 1.6 mEq/L alkalinity is 77.5% for 22.5% error. I think that amount is OK for ROM mental calculations but 22.5 out of 100 is only 13 dB signal to noise ratio. Not so impressive.